Twisting of textile filaments



United States Patent 2,936,561 rwisriNG F TEXTILE mAMENrs John PercivalRussell,l Croesyceiliog, Cwmbran Eric Stutchfield,` West lfontnewydd,'Cwmbram John Ralph Myers, Croesyceiliog, Cwmbran, and David FoxallArthur, West Pontnewydd, Cwmbran, England, assignltrlilidto ,BritishVNylon Spinners Limited, Pontypool, Eng- `Appiieiiiimirpiy z, 1956,serial No. 595,543 claims priority, application Great Britain July 19,195s 4 claims. (ci. `5'/'11.4)

.very many years, and of late they have been found par ticularlysuitable for use in crimping thermoplastic textile lfilaments by atwisting, setting, and back-twisting se- :quence. It will be appreciatedthat a fase-twist-tube nables such a crimping operation to be carriedout in continuous fashion,I instead of in separate steps, as in the casewith certain other crimping processes. Heat is applied to the filamentswhile they are in thehighly-twisted ycondition to set this twist, sothat when the equal and opposite twist of the untwisting occurs afterthe lament's -leave the twist tube, crimpingoccurs.

Th@ Principle 1111011 which all known false-twist-tubes i" have operatedis to cause the running filaments to acquire the rotational motion ofthe tube by means providing for contact with a part or parts of theinside of the tube whereby each revolution of the' tube applies onerevolution to "the filaments. ,Thus the laments may be caused to passround a pin orpulley wheel mounted within the tube across the axisthereof or trapping means may be provided ,tortrap them against one sideof the tube. Alternatively, ,fthe bore of the tube itself may be madeeccentric over fsome part of its length so that .the filaments arecaused to acquire the rotational motion of the tube by taking a `4shortpath away from the axial line. In other tubes, the laments enter througha radial hole at one end of the Qtube, i.e. through a hole displacedlradially from the axis ofthe tube.

`In the process wherein a running textile filament is crimped by meansof a false-twist-tube, a very high de- --gree of twist is required; forinstance, 90 turns per inch is by no meansextraordinarily high, althougharound textile filament and having its internal surface, at least at oneend thereof, composed of a non-abrasive material having a high coeicientof friction with the textile filament required to be twisted thereby.The invention also comprises a process whereby a false twist is impartedto a running textile filament by causing the filament to bear against,and be rotated by, the inner peripheral surface of one end, at least, ofa twist-tube, and on one side of the axis thereof, the internal surfaceof the tube et that one end at least being composed of a non-abrasivematerial having a high coefcient of friction with the filament. Theinvention also comprises the crimping of a thermoplastic textilefilament by such a process, wherein the filament is heated oversucceeding lengths of itself which are in the highly twisted conditionto an extent sufficient to set the twist therein, the succeeding lengthsof twist-set filament are then cooled before untwisting, andthe'untwisted filament is wound up under low tension in crimped form.

According tothe invention, the filament is twisted by direct frictionalcontact with the inner peripheral surface of the tube, and thus, if thefilament is held steady in the same relative position on the peripheryof the tube, the ratio of the rotational speed of the filament to thatof the tube will depend on the ratio of the inner diameter of the tubeto the diameter of the filament. It follows that, as this last ratiowill be relatively large, say, of the order of 250 to 1, for a givendegree of twist and a given throughput, the speed of the twist-tube can,be considerably reduced in comparison with a twist-tube operatingaccording to the conventional principle in which one rotation of thetube is never capable of inserting more than one twist in the filamentpassing through it. Furthermore, a considerably enhanced throughput canbe achieved at relatively moderate rotational speeds of the twist-tube.

By a material having a high coefficient of friction with the textilefilament is meant not only a material which, per se, has such acoefficient of friction, but also material which by reason of itssurface characteristics and/or resilience has such a coefficient inpractice, i.e. under operating conditions for any particular textilefilament as held against the material by its own tension or by othermeans.

As examples of materials which may be used to line the twist-tube,various sorts of rubber are suitable to a higher or lo-Wer degree, butthe most eminently satisfactory material is natural rubber with carbonblack filler. This material attains a polished condition after a certainamount of use, which appears to confer the necessary frictionalqualities combined with resistance to wear, which are the criticalfeatures for a successful material. The filament is caused to bearagainst the inner periphery `of the twist-tube on one side of the axis.thereof by 75, turns per inch satisfactory .for most multilament yarnslof between SO'andV 100 denier. 'Thus in order .that the processV shallbe reasonably productive it .has .beennecessary to rotate the tube atvery high speeds, and

-speeds of the order of 30,000 rpm. are often used. As

:an example, in order that nylon continuous filament yarns :shouldberrimpled and woundupat a speed of 33 feet per minute, a rotationalspeed of 28,000 rpm. has been necessary. Such high rotational speeds ofthe twist-tube obviously create difficulties relating to theirconstruction fand maintenance, and it is the object of the presentinvention 'to achieve'a satisfactory fand, indeed, enhanced`=productivity of crimped yarnl at considerably lower rota-"tiorialfspeeds of the twist-tube.

comprises ta' .twist-tube Jfor imparting Ya false twistA toma leading ittowards and/or away from the tube to a guide,

or guides, the path between the end of the tube and the guide or guidesbeing at an angle (up to approximately `a rightV angle) to theprojection of the axis of the tube.

It is necessary in the first caseto ensure that the correct amount ofpre-tensioning has been applied to the filament. The correct angle andpre-tension for each filament can best be discovered empirically, and itshould be such that some little slip occurs between the periphery andthe filament, which condition, besides-representing the optimum fortwisting effect, is also consonant with no damage to the filament. lfthe slip is allowed to be too great, damage may occur. Tensions such asare used in any normal false twist crimping process are satisfactory`and must be such as to hold thevlilainent firmly 0 A'I`his'object isachieved by thepresent inventionwhich ..7

against the inner periphery of the tube without jumping. One embodimentof the invention will now 'be described with reference t0 theaccompanyingdrawings, in 'which Figure 1 is a section through a twisttube according to the invention; and Y Figure 2 is a sketch showing theuse of a twist-tube according to the invention in a process for crimpinga thermoplastic, textile filament. l

Referring particularly to Figure 1, the twist-tube comprises a iixedannular portion 1 and a driven annular portion 3 mounted on rollerbearings 5, 7 therein. The driven annular portion 3 is rotated by band9. Fitted within the driven annular portion 3 is a rubber bush 1l, theinner surface of which makes direct Contact with the yarn 13. The yarnis led to the tube at an angle to the axis thereof, and led away fromthe tube over a pulley 15, at a similar angle to the axis of the tube.Thus the yarn when suitably tensioned is kept in contact with the wholelength of the inner surface of the rubber bush, and `also with the twocurved end portions thereof. The dimensions of a twist-tube which havebeen found to be satisfactory in practice, are as follows:

Referring now to Figure 2, a yarn 13V of thermoplastic material iswithdrawn over one end of a supply package 17, and is then passed aroundthe drum of a magnetic hysteresis tensioner 19 which imposes a constantoutput tension on the yarn. The yarn is then led through an infra-redheating device 2l comprising a glass tube 23 having electric resistancecoils 25 wound therearound. The device is sutlciently long to ensurethat the twist in the thermoplastic yarn may be set by means of the heatproduced by it at the high values of yarn throughput possible in thisinvention. After passing through the tube, the yarn travels through theair for a suicient time vfor it to 'cool below its plastic state, andthen passes into Vone end of a twist-tube 27 such as that illustrated inFigure l. Thettwist-tube is mounted with its axis at an angle to thevertical such that the yarn led directly through and from the heatingdevice makes contact with one side 29 of the inner peripheral surface ofthe rubber Vbush contained within the twist-tube.

The yarn is 'led from the twist-tube around a pulley-wheel 31, whichensures contact of the yarn with the bush at this end thereof, andtherefore along the whole length of the bush. It is a question ofexperiment to tind the most suitable .angles of entry and exit of theyarn, and they will depend mainly. on the denier of the yarn and thenumber of turns per inch of twist it is desired to insert in it. Ingeneral, however, it may be stated that angles between 45 and 90 arerequired, the greater angles imparting vhigher vtwist than the lesser.The angles referred to are that between the yarn entry path and theprojection of the axis of the twist-tube, and that between the yarn exitpath and the projection of the axis of the tube. After passing over thepulley-wheel 31 the yarn is led through the nip of a pair of forwardlyrolls 33, 35 which feed the of turns per inch of twist inserted in theyarns is very little affected by variations in tension or speed of theyarn, or by variations in speed of the tube above the critical speed, orby the amount of wear of the material forming the inner surface of thetube. The reason for this is that, naturally, for crimping purposes, thenumber of turns per inch will be high, and, at these high values, theincrease in torque to be imparted to the yarn to raise the number ofturns per inch by, say, 5%,.will require to besomething of the order of30%. Thus the settings of tube speed, and yarn tension and speed are notlrequired to be controlled within very narrow limits, as in some otherprocesses.

The minimum angular velocity, in revolutions per minute, of the twisttube can be ascertained from the formula:

V`=T t 121ty RM where Y t is the speed of the textile filament in feetper minute.

yarn forward at a slightly greater speed than that at I,

kwhich it is eventually wound up lby the roll 37 on the package 39. Thusthe yarn between the rolls 33, 35 `and the wind-up package 39 is relaxedslightly. In operation, the yarn is given a high degree of falsetwist bymeans of the twist-tube, which high twist in one direction feeds backthrough the heating device to the tensioning device, and `is set; theyarn in its twist-set condition is allowed top cool ysomewhat betweenthe heating device and the Vtwist-tube; twist in the opposite sense isimparted to the `twist-set yarn directly on leaving the twist-tube; andthe now crimped yarn is Wound up under a low tension.

VWe have found that, using an apparatus according Vto VVthe invention,as generally described above, in a process ,for crimping `rnultifilamentyarns of, for example, poly- Yhexamethylene adipamide, once the twisttube is rotating et or above a given minimum angular velocity, the valueTurns per inch Ry is the radius of the textile filament in inches. RM isthe internal radius of the twist-tube in inches.

Furthermore, the apparatus produces a textile filament, of a givennature, of constant twist factor (i.e. turns per inch multiplied kby thesquare root of the denier), for example, of the order of 680 orthereabcutsl for polyhexamethylene adipamide yarn comprising filamentsof v3 denier each, so that once the apparatus is arranged to give theoptimum twist to sucha textile filament of a certain denier, it will becorrect also for imparting the optimum twist to such filaments of anyother denier.

To illustrate the variation in turns per yinch of twist with denier,the'followingv table shows `the inter-relation of these two factors onmultifilament yarn of polyhexamethylene adipamide, with a tube rotatingat 15,00 r.p.m., tension on the yarn of 25 grams, and a throughput of170 feet per minute. kthe tube at the same side of the axis thereof, atan angle vof 45 to the axis of the tube. v

TABLEl Yam Denier 21o 15oV 100 7o eo 45 so 'ramper inch 42 55 1o sa as103l 125 the axis thereof atan angle of 45 to the axis ofthe tube.

TABLE 2 Throughput in teet/mlni As examples of the use of the twist tubeof the vinvention in processes for crimping multilament yarn oflpolyhexamethylene adipamide inV a continuous fashion, the

Y following process conditions are given in VExamples `l 31o 1 1inclusive:

Example 1 Multlament yarn from asnpply Ypackage is 4.led

through a tensioning device, such as amagnetic hysteresis type andthence over and in contact with a metal plate, electrically heated to23.5 C., to thc twist-tube `which. 'is rotating at 1'50.0;r.p.m. Guidesare so positioned;v above and below the twist-tube, wvhose .axisfof:rotation is The yarn enteredand left cal, that the yarh entersandfleaves the tube, at'one side of the axis thereof, at an angleof 45to the axis of the tube. Under the above conditions', yarn may beprocessed at speeds between 2O and 60 feet/minute, and wound up onapackage under low tension.

Examples 2 to 9 The process of Example l is carried out'on 30 and 60denier multiilarnent yarn but this is heated while in the highly-twistedcondition by means of radiant heat within a tube, throughthemiddle ofwhich the yarn passes, instead of by contact with the hot metal plate.The tube is 25 cms. longV and made of glass and the heat lis generatedby an yelectric resistance wire coiled around the outside of it. Thetemperatures expressed are those recorded by a thermocouple inequilibrium in the yarn path the tube, and are the maximum temperaturesso recorded.

i Through- Temper- VExample No, Yarn A putin Tension, ature,

' Denier feet] grams C.

minute so 205 6.5 534 60 205 22.0 413 60 500 5.5 545 60 300 23.0 545 30200 3.5 55s 30 200 19.0 55s 30 500 3.5 41s a 300 21.0 419 Example 10 150denier multifilament yarn was crimped by a process similar to thosedescribed for Examples 2 to 9 above, except that the heater tube wasonly 13 cms. long. The maximum temperature within the tube was 705 C.,and the crimped yarn was produced at a speed of 200 feet/ minute, withan ingoing tension of 24 grams.

Example 11 60 denier/ 10 filament yarn of polyhexamethylene adipamide isled from a supply package, through a magnetic hysteresis tension devicewhich imposes an output tension of 25 grams on it, to the twist-tuberotating at 4000 r.p.m., and enters at an angle of 80 to the projectionof the axis of the twist-tube. Positioned between the tension device andthe twist-tube, so as to heat the yarn passing through it in itshighly-twisted condition, is an infra-red heater 3 feet in length. Theheater comprises a rod-like electric heating element positioned alongone focus of an elliptical cross-section reflector tube surrounding it,and the yarn passes along the other focus of the ellipse. rIhetemperature within the tube is 224 C., as measured by a thermocouple inequilibrium in the yarn path within thev tube. The yarn leaves thetwist-tube at `an angle of 80 to the projection of the axis thereof andis wound up under low tension at a speed of 200 feet/ minute.

Example 12Y Polyhexamethylene adipamide monoiilament of l denier isprocessed in continuous fashion by a twist-tube of the invention and inaccordance with the arrangements of Example 11, except that thepre-tension imposed upon it is less than 2 grams, and the twist-tube isrotated at 4,600 r.p.m. A twist-lively filament is thus produced havingsome 20 turns per inch inserted, set, and removed in continuous fashion.The twist factor is low in this case owing to the dilerent frictionalnature of the surface of the monofilarnent, and owing to the greatertorque needed to insert a given twist in such an elemental structure asa monolament than is required for a multiiilament yarn.

Example 13 50 denier multilament yarn of the synthetic linear polyestersold as Terylene (registered trademark) was crimped in accordance withvExample ll', 'but with the twist-tube rotating at 4,600 r.p.m.

` It should be stressed that, in all the above examples, the yarn shouldundergo a suicient amount of cooling after heating and before untwistingto ensure that 'it is not in a plastic condition such that actualdeformation 'of it will occur during untwisting. A suicient `spacebetween heater and twist-tube, in which the yarn passes through theambient atmosphere, will provide the conditions for this cooling. Itshould also be mentioned that, if the twist-tube itself is suitablymounted sothat its axis is inclined to Vthe vertical by the requisiteangle,` say 45, as shown diagrammatically in Figure 2, a convenienthorizontal disposition of the ,several pieces of apparatus can beachieved.

Although electrical heating by contact or radiation has been describedfor setting, such can also be achieved by pressure steam, or by contactwith heated solid particles, such as glass, in uidized condition broughtaboutby the passage of air therethrough. The twist-tube of the inventionhas one further great advantage over those previously known, in that itis capable of imparting a false twist to several textile lilaments atonce. Guides may be so positioned at the entrance to and exit from thetube that a number of textile filaments may be maintained in contactwith different relative positions of the inner periphery of the tube.Thus, two, three, four or more textile filaments can be processedsimultaneously, and this added productivity of the invention furtherincreases its usefulness over the conventional false twist-tube andprocesses utilizing the same. Furthermore, by a suitable arrangement ofsupply and wind-up packages and guides, it is possible to impart falsetwist of differing senses to a. plurality of textile laments, and to plyoppositely initially-twisted textile filaments together to producebalanced yarns. In this case, some textile iilaments will pass throughthe tube in one direction, and some in the other; or one in onedirection, and one in the other.

Suitable thermoplastic textile filaments for crimping include those ofthe synthetic linear polymeric amides or esters, such as nylon orTerylene (registered trademark), and those of cellulose acetate andtriacetate. It is also possible to crimp non-thermoplastic textile tlaments which have been treated with a thermosetting agent. If the textilefilament to be crimped is a monoiilament, it will not be practicable ornecessary to impart such a high number of turns per inch of twist as fora multiflament yarn. Useful monolaments of a twistlively, rather thancrimped, nature may be produced with a twist of from 20 to 30 turns perinch, or there abouts, which iilaments may be incorporated in fabrics insuch a way as to impart stretching to those fabrics.

Finishing of articles containing yarns crimped according to thisinvention may be carried out in similar manner as for any known crimpedyarns produced by twisting, setting and back-twisting. However, owing tothe relatively far higher speed of production of the yarns according tothe invention, it may be advantageous to develop the bulkiness andstretchiness of the articles somewhat more slowly, and a convenient timefor doing this is provided by the normal scouring ltreatment in liquidup to, say, 50 C. in temperature.

What we claim is:

l. Apparatus for imparting false twist to textile laments comprising arotatable member having an axial bore with outwardly ared ends extendingtherethrough, means guiding a textile filament to one end of said borealong a path angulated with respect to the bore axis of the order ofbetween 45 and 90, and means guiding the textile filament from the otherend of said bore along a path angulated with respect to the bore axis ofthe order of between 45 and 90, the interior surface of said bore, atleast at the liared ends thereof, being composed of a non-abrasivematerial having a high eot 7 efficient of friction with the textilelament, and ythe diameter of said bore exceeding the diameter of saidfilament, whereby a plurality of turns of false twist is imparted to thefilament for each revolution of said rotatable member.

2. Apparatus as dened in claim 1, wherein said rotatable member ismounted on a txed annular member 'by means of an anti-friction bearing.

3. Apparatus as detinedrin claim 1, wherein the interior surface of saidbore comprises a bush composed of natural rubber with carbon black ller.

4. Apparatus for imparting false twist to textile ilaments comprising asequential arrangement of filament lsupply means, tensioning means,heating means, twisttube and guide means, said twist-tube including arotatable member having an axial bore with outwardly `flared endsextending therethrough, the interior surface of said bore, at 'least theflared ends thereof, being composed of a non-abrasive material having ahigh coef.- cient of friction with the textile filament, and thediameter of said bore exceeding the diameter of said lilament, whereby aplurality of turns of false twist is im,- parted to the iilamentvfo'reach revolution of said roe tatable member, the axis of said rotatablemember being angulated with respect to the lament path from `saidheating means to said twist-tube and the lament path from saidtwist-tube to said guide means.

References Cited in the le of this patent UNITED STATES PATENTS2,475,922 Stockly July 12, 1949 2,753,679 Von Schmoller et al. 7...-July 10, 1956 2,823,513 Vandamme et al. Feb. V18, 1958 FOREIGN Y PATENTS154,341 Austria Sept. 26, 1938 440,546 Italy Oct. 13, 1948 (Addition toPatent 399,231) 472,583 France Aug. 11, 1914 496,585 Great Britain Dec.2, 1938 500,823 Great Britain Feb. 16, 1939

